Selenium rectifiers



United States Patent SELENIUM nncrrrrnas Eric Lionel French, London, England, assignor to Westinghouse Brake and Signal Company Limited, London, England No Drawing. Application June 13, 1956, Serial No. 591,026

Claims priority, application Great Britain June 15, 1955 Claims. (Cl. 317241) My invention relates to selenium rectifiers of the kind in which an artificial or non-genetic barrier layer is provided between the selenium and counterelectr-ode layers.

According to the invention, in a rectifier of the kind described, the non-genetic layer consists of a prolamine or mixture of two or more prolamines.

According to one method of putting the invention into effect a partly formed element consisting of a base plate having a layer of selenium applied to it, the selenium being in its crystalline form, is immersed for one minute in a one percent solution by weight of zein dissolved in an alcohol-water solvent mixture. Suitable alcohols are methyl, ethyl and isopropyl alcohols and their proportion in the alcohol-water mixture may vary between 80 to 90 percent. If ethyl alcohol is used, the solution is preferably maintained at a temperature of 70 C. The plate is then removed from the solution, being arranged with its plane vertical and being withdrawn vertically at a rate of six inches per minute. The temperature at which the dipping is performed and the rate of withdrawal are so chosen that the solvent evaporates almost completely and the plate is dry in appearance within a few seconds of its being withdrawn from the solution. The proportion of Zein may be varied within limits: with a proportion of 0.5 percent the effect of the process upon the rectifier becomes seriously impaired, probably because the layer becomes too thin, and at a proportion of 10 percent the effect of increasing the proportion becomes insignificant so far as reverse resistance is concerned.

In order to insure complete evaporation of the water the plate is preferably exposed to radiant heat for a few minutes after its withdrawal from the solution.

The rate of evaporation also depends upon the ambient temperature and the rate of flow of air past the plate while it is being withdrawn from the solution. The procedure set out above has been found suitable for use in a room at a temperature of C. and having a normal degree of ventilation, the resulting rectifier having a nongenetic layer of such thickness that the forward resistance of the rectifier is of reasonable value. Variation in any of the conditions results in a change in this forward resistance but, in practice, it has been found convenient to vary the thickness of the layer by variation in the concentration of the solution, all other conditions being maintained constant. The effects of variation of these other conditions are complex, :but are similar to those well known in the art of forming paint film.

After the plate has dried completely the counterelectrode is applied and the element electro-formed in known manner.

During the application of the zein the base plate neces- 2,802,974 iatented Aug. 13, 1957 sarily becomes covered with a film of this material, but the tilm is so thin that its resistance is small and the forward resistance is not increased unduly.

Other prolamines which may be used in place of zein are hordenin and insulin. Alternatively, a mixture of two or more of these substances may be used.

Although I have herein described several methods of forming a barrier layer on the selenium layer of a rectifier cell, it is to be understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

l. A selenium cell comprising, a base plate, a selenium layer thereon, a non-genetic layer of prolamine on said selenium layer, and a counterelec-trode on said non-genetic layer.

2. A selenium cell comprising, a base plate, a selenium layer thereon, a non-genetic layer of one or more prolamines from the group comprising zein, hordenin and insulin on said selenium layer, and a counterelectrode on said non-genetic layer.

3. A selenium cell comprising, a base plate, a selenium layer thereon, a non genetic layer of zein on said selenium layer, and a c-ounterelectrode on said non-genetic layer.

4. A selenium cell comprising, a base plate, a selenium layer thereon, a non-genetic layer of hordenin on said selenium layer, and a counterel'ectrode on said nongenetic layer.

5. A selenium cell comprising, a base plate, a selenium layer thereon, a non-genetic layer of insulin on said selenium layer, and a counterelectrode on said nongenetic layer.

6. In a method of manufacturing selenium cells, the step of applying to the selenium layer on a base plate a solution containing between 0.5 and 10.0 percent by weight of prolarnine in an alcohol-water solvent solution, to form a non-genetic layer on the selenium layer.

7. In a method of manufacturing selenium cells, the step of applying to the selenium layer on a base plate a solution containing between 0.5 and 10.0 percent by weight of one or more prolamines from the group comprising zein, hordenin and insulin in an alcohol-water solvent solution, to form a non-genetic layer on the selenium layer.

8. In a method of manufacturing selenium cells, the step of applying to the selenium layer on a base plate a solution containing between 0.5 and 10.0 percent by weight of zein in an alcohol-water solvent solution, to form a non-genetic layer on the selenium layer.

9. In a method of manufacturing selenium cells, the step of applying to the selenium layer on a base plate a solution containing between 0.5 and 10.0 percent by weight of hordenin in an alcohol-water solvent solution, to form a non-genetic layer on the selenium layer.

10. In a method of manufia-cturing selenium cells, the step of applying to the selenium layer on a base plate a solution containing between 0.5 and 10.0 percent by weight of insulin in an alcohol-water solvent solution, to form a non-genetic layer on the selenium layer.

References Cited in the file of this patent UNITED STATES PATENTS 2,481,739 Goodman 'Sept. 13, 1949 

1.A SELENIUM CELL COMPRISING, A BASE PLATE, A SELENIUM LAYER THEREON, A NON-GENETIC LAYER OF PROLAMINE ON SAID SELENIUM LAYER, AND A COUNTERELECTRODE ON SAID NON-GENETIC LAYER. 